Redox Equations

Name Class DateProblem Solving continued2. Assign oxidation numbers to each element.42 0 2 21 2 21Ni O2 Fe → Ni 2 2OH Fe 2 2OH Delete any ions or molecules in which there is no change in oxidation state.4Ni O2 Fe0 2 2→ Ni 2 Fe 23. Write the half-reaction for reduction.4 2Ni O2 → Ni 2Balance the mass by adding OH and H 2 O.4 2Ni O2 2H 2 O → Ni 2 4OH Balance the charge by adding electrons to the side with the higher positivecharge.4Ni O2 2H 2 O 2e 2→ Ni 2 4OH 4. Write the half-reaction for oxidation.Fe0 2→ Fe 2The mass is already balanced.Balance the charge by adding electrons to the side with the higher positivecharge.Fe0 2→ Fe 2 2e 5. The numbers of electrons lost and gained are already the same.6. Combine the half-reactions.4Ni O2 2H 2 O 2e 2→ Ni 2 4OH Fe0 2→ Fe 2 2e NiO 2 2H 2 O Fe → Ni 2 Fe 2 4OH 7. Combine ions to change the equation back to its original form. The four OH ions combine with the nickel and iron to make nickel(II) hydroxide andiron(II) hydroxide.NiO 2 2H 2 O Fe → Ni(OH) 2 Fe(OH) 2Check the balance.EVALUATEAre the units correct?NAIs the number of significant figures correct?NAIs the answer reasonable?Yes; the reaction has the reactants and products required and is balanced.Copyright © by Holt, Rinehart and Winston. All rights reserved.Holt ChemFile: Problem-Solving Workbook 309 Redox Equations